Abstract
RNA interference (RNAi) is a sequence-specific down-regulation in the expression of a particular gene, induced by double-stranded RNA (dsRNA). Feeding of dsRNA either directly or through transgenic plants expressing dsRNA of insect genes has been proven successful against lepidopteran and coleopteran pests, establishing an additional alternative to control insect pests. Lepidopteran crop pests including Spodoptera litura (Fabricius) (Noctuidae), Chilo partellus (Swinhoe) (Crambidae), Plutella xylostella (Linnaeus) (Plutellidae), and Maruca vitrata (Fabricius) (Pyralidae) are the devastating pests of a variety of crops. To tap the potential of RNAi against insect pests, a gene coding for the key enzyme in chitin biosynthesis in arthropods, the chitin synthaseA (CHSA), has been targeted through an exogenous delivery of dsRNA and plant-mediated RNAi. The introduction of dsCHSA caused “Half ecdysis” and “Black body” type lethal phenotypes and a significant reduction in larval body weight. Subsequent RT-qPCR analysis demonstrated the down-regulation of CHSA gene transcripts from 1.38- to 8.33-fold in the four target species. Meanwhile, when S. litura larvae fed with leaves of transgenic tobacco plants expressing dsSlCHSA, the mRNA abundance of CHSA gene was significantly decreased resulting in lethal phenotypes like “Double head formation,” “Half ecdysis,” and “Black body.” In addition, abnormalities in pupal–adult and adult stage were also documented, strongly suggesting the RNAi effect of CHSA gene at late developmental stages. Overall, the results demonstrated that CHSA gene expression in Lepidopteran crop pests could be suppressed by application of dsRNA either as feeding or through transgenic crop plants.
Highlights
Lepidopteran crop pests including tobacco cutworm, Spodoptera litura (Fabricius) (Lepidoptera: Noctuidae); maize/sorghum stem borer, Chilo partellus (Swinhoe) (Lepidoptera: Crambidae); diamondback moth, Plutella xylostella (Linnaeus) (Lepidoptera: Plutellidae), and legume pod borer, Maruca vitrata (Fabricius) (Lepidoptera: Pyralidae) are considered as most destructive pests of several economically important agricultural and horticultural crops worldwide
There were nucleotide variation at 143, 338, 355, 383, and 415 bp positions among the amplified sequence of chitin synthaseA (CHSA) from S. litura, C. partellus, P. xylostella, and M. vitrata and rest other sequences were similar to the reference sequence of S. litura CHSA (Supplementary Figure S3)
This study offers new insights to explore the potential of double-stranded RNA (dsRNA)-transgenic plant-mediated RNA interference (RNAi) and design strategy for management of four key lepidopteran crop pests, viz., S. litura, C. partellus, P. xylostella, and M. vitrata
Summary
Lepidopteran crop pests including tobacco cutworm, Spodoptera litura (Fabricius) (Lepidoptera: Noctuidae); maize/sorghum stem borer, Chilo partellus (Swinhoe) (Lepidoptera: Crambidae); diamondback moth, Plutella xylostella (Linnaeus) (Lepidoptera: Plutellidae), and legume pod borer, Maruca vitrata (Fabricius) (Lepidoptera: Pyralidae) are considered as most destructive pests of several economically important agricultural and horticultural crops worldwide. The most common method for the management of those insect pest is the use of insecticides or bio-control agents Bacillus thuringiensis (Bt) toxins. The management of those insect pests is a daunting task because of the development of resistance against insecticides and Bt toxins (Storer et al, 2010). These problems necessitate finding an alternative pest control strategy to supplement the present pest management methods. RNA interference (RNAi)-based strategy through the expression of double-stranded RNA (dsRNA) targeting potential genes in crop pests has paved the way for new generation of integrated pest management (IPM). The comparative analysis to study the effect of RNAi among crop pests belonging to different families in lepidopterans has not been appeared so far
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